The present invention relates generally to vehicle navigation systems. More specifically, the invention relates to methods and apparatus for generating maneuvers for an intersection having a turn-lane connector.
A conventional vehicle navigation system generates route and direction information to a driver. To provide the route information, the conventional vehicle navigation system includes a route generator, or equivalent, which reviews a map database and calculates a route based on a provided source and destination. To provide direction information, the conventional vehicle navigation system also includes a maneuver (or direction) processor, or equivalent, which monitors the vehicle's location with respect to the generated route and provides maneuver indications to the driver, as appropriate, directing the driver to the desired destination.
The operation of a conventional maneuver processor is described in the following. When the generated route includes a turn at the intersection of two roads, for example, the maneuver processor provides a turn indication to the driver as the vehicle approaches the intersection according to the general direction of the turn (e.g., left or right) and the angle between the entry road and the exit road as represented in the map database. For example, where the general direction of the turn is "right" and the angle between the entry street and the exit street is approximately 90 degrees, the maneuver processor provides a simple "right turn" indication to the driver. Where, on the other hand, the angle between the entry and exit roads is much greater than (or less than) 90 degrees, the maneuver processor provides a "slight right turn" ("hard right turn") or "keep right" ("sharp right") maneuver indication instead. The maneuver processor also provides the name of the exit road to facilitate the correct execution of the maneuver.
The maneuver indication provided to the driver may be in various forms, including, but not limited to, a pre-recorded voice prompt, a visual icon provided on a display device, highlighted text provided on a display, or some combination of the above. The maneuver processor also includes means for ensuring that the maneuver indication is provided to the driver sufficiently in advance of when the maneuver is required.
When the generated route includes navigating through an intersection that is relatively complex as compared to the simple example described above, the driver requires a maneuver indication which is unambiguous, which suggest to the driver how the maneuver is to be executed, and which is consistent with what the driver observes at the intersection. Accordingly, the conventional maneuver processor is adapted to provide a maneuver indication that reflects as closely as possible the actual arrangement of roads at an intersection. This requirement is typically satisfied by providing a maneuver indication which corresponds in angle or shape with the maneuver to be performed by the driver. In some embodiments, this capability is manifest by providing a maneuver indication which includes highlighted portions of a map. In other embodiments, the maneuver indication includes one or more displayed icons which closely approximate the turn angles of the maneuver.
Occasionally, the capability of the conventional maneuver processor to provide a maneuver indication that closely reflects the actual arrangement of roads at the intersection causes it to provide a maneuver indication that includes unnecessary or redundant information, or that is inconsistent with what the driver actually sees as he/she approaches the intersection. An example of this is depicted in FIGS. 1(a) and (b).
FIG. 1(a) is a representation of an intersection 10 comprising cross-streets, 12 and 14, depicted as N/S street 12, and E/W street 14, respectively. Intersection 10 also includes a turn-lane 16 that connects the northbound traffic on N/S street 12 to the eastbound traffic of E/W street 14. The intersection 10 is represented in the map database as shown in FIG. 1(b), including a road 12' corresponding to N/S street 12, a road 14' corresponding to E/W street 14, and a connector 16' corresponding to turn lane 16. In this case, the conventional maneuver processor operating in the manner described above generates a double maneuver indication for a right turn through the intersection as shown in the figure. That is, the maneuver processor generates a "slight right" indication 18, or its equivalent, for the maneuver from road 12' onto connector 16', followed immediately by a second "slight right" indication 20, or its equivalent, for the maneuver from connector 16' onto road 14'.
When the distance between the entry of turn lane 16 and the junction of cross-streets 12 and 14 is relatively short, the driver approaching intersection 10 from the south only sees the junction of E/W street 14 with N/S street 12, and does not see the turn lane 16. So, when the double maneuver indication is provided in advance of the intersection, the driver is confused by the maneuver indications which do not match the driver's perspective. The driver's confusion is exacerbated by the fact that the turn lane 16 usually has no road name (i.e., the first "slight right" maneuver indication provides no exit road name for the driver). Therefore, it would be preferable in this case for the maneuver processor to provide a simple "right turn" indication to the driver indicating a maneuver from N/S street 12 onto E/W street 14 regardless of whether or not the driver uses the turn lane.
Another case where the conventional maneuver processor provides a maneuver indication including unnecessary or redundant information, or that is inconsistent with what the driver actually sees upon approaching the intersection is depicted in FIGS. 2(a) and (b). FIG. 2(a) is a representation of a three-way "T" intersection 22 comprising N/S street 24 and abutting street 26. As shown in the figure, N/S street 24 includes a median 28 and a turn lane 30 for allowing access to abutting street 26 from the northbound portion of N/S street 24. The intersection 22 is represented in the map database as shown in FIG. 2(b), which includes a road 24' corresponding to the northbound portion of N/S street 24, a road 24" corresponding to the southbound portion of N/S street 24, a road 26' corresponding to abutting road 26, and a connector 30' corresponding to turn lane 30. In this case, the conventional maneuver processor generates a double maneuver indication for a left turn from N/S Street 24 onto abutting street 26 as shown in the figure. That is, the maneuver processor generates a "slight left" indication 32, or its equivalent, for the maneuver from road 24' onto connector 30', followed immediately by a second "slight left" indication 34, or its equivalent, for the maneuver from connector 30' onto road 26'. As can now be appreciated by the reader, the double maneuver indication is potentially confusing to the driver. Therefore, it would be preferable in this case for the maneuver processor to provide a simple "left turn" indication to the driver indicating a maneuver from the northbound lane of N/S Street onto abutting street 26.
Another case where the conventional maneuver processor provides a maneuver indication which includes unnecessary or redundant information, or which does not conform with what the driver actually sees is depicted in FIGS. 3(a) and (b). FIG. 3(a) is a representation of an intersection 36 including N/S street 38, east street 40, and west street 42. N/S street includes a median 44. The intersection 36 is represented in the map database as shown in FIG. 3(b) which includes a road 38' corresponding to the northbound portion of N/S street 38, a road 38" corresponding to the southbound portion of N/S Street 38, a road 40' corresponding to east street 40 which abuts road 38' and which connects road 38' to road 38", and a road 42' corresponding to west street 42 which abuts road 38". In this case, the conventional maneuver processor provides a double maneuver indication for a left turn from the northbound portion of N/S street 38 as shown in the figure. That is, the conventional maneuver processor provides a "left turn" indication 46, or its equivalent, for the maneuver from road 38' to a connecting portion of road 40', followed immediately by a "straight" indication 48, or its equivalent, to indicate the passage from the connecting portion of road 40' onto road 42'. As can now be appreciated by the reader, the double maneuver indication includes information which is redundant and unnecessary. (A similar problem occurs when, as shown by the dashed-line, the conventional maneuver processor provides a double maneuver indication for a U-turn from the northbound portion of N/S street 38 i.e., road 38'! onto the southbound portion of N/S street 38 i.e., road 38"!.) It would be preferable in this case for the maneuver processor to provide a simple "left turn" (or "U-turn") indication to the driver indicating a maneuver from the northbound portion of N/S street 38 onto West street 42.
FIGS. 4(a) and (b), depict yet another case where the conventional maneuver processor provides a maneuver indication which includes unnecessary or redundant information, or which does not conform with what the driver actually observes at the intersection. FIG. 4(a) is a representation of street 50 wherein the northbound portion of the street 52 is separated from the southbound portion of the street 54 by a median 56. The street 50 is represented in the map database as shown in FIG. 4(b), which includes a road 52' corresponding the northbound portion of the street 52, a road 54' corresponding to the southbound portion of the street 54, and a connector 58 between them representing a U-turn lane. In this case, the conventional maneuver processor generates a double maneuver indication for a U-turn as shown in the figure. That is, the conventional maneuver processor provides a "left turn" indication 60, or its equivalent, for the maneuver from road 52' onto connector 58, followed immediately by another "left turn" indication 62, or its equivalent, for the maneuver from connector 58 onto road 54'. Here, as the reader can appreciate, it would be preferable in this case for the maneuver processor to provide a simple "U turn" indication, or its equivalent.